A new Monte Carlo simulation method for studying three-dimensional microstructures as well as their evolution in polycrystalline materials has been set up. The algorithm is simple and flexible to apply. With the present method, kinetics of three-dimensional grain growth is accurately reflected and the simulation efficiency is greatly improved. The simulation can not only be used reliably to analyze quantitatively the microstructures and their evolution, but also be used conveniently to observe microstructures as well as their evolution on the horizontal section and the sections at any angle to the horizontal plane, to measure the characteristic parameters in three dimensions and cross-sections, together with their relationships between the two systems, and to many other aspects. A new Monte Carlo simulation method for studying three-dimensional microstructures as well as their evolution in polycrystalline materials has been set up. The algorithm is simple and flexible to apply. With the present method, kinetics of three-dimensional grain growth is accurately reflected and the simulation efficiency is greatly improved. The simulation can not only be used reliably to analyze quantitatively the microstructures and their evolution, but also be used conveniently observe microstructures as well as their evolution on the horizontal section and the sections at any angle to the horizontal plane, to measure the characteristic parameters in three dimensions and cross-sections, together with your relationships between the two systems, and to many other aspects.